convert raster font image to array of bitmask bytes

png2font.php

<?php
$infile = $argv[1]; // font image file name
$w = $argv[2]; // font char width
$h = $argv[3]; // font char height
$color_x = $argv[4] ?? 0; // x coordinate of font color sample
$color_y = $argv[5] ?? 0; // y coordinate of font color sample

$img = imagecreatefrompng($infile);
$img_w = imagesx($img);
$img_h = imagesy($img);

$color = imagecolorat($img, $color_x, $color_y);

echo "img w: $img_w, h: $img_h\n";
echo "char w: $w, h: $h\n";
echo "color: $color\n";

$chars = [];

for ($pos_y = 0; $pos_y < $img_h; $pos_y += $h) {
	for ($pos_x = 0; $pos_x < $img_w; $pos_x += $w) {
		for ($span_y = 0; $span_y < $h; $span_y++) {
			$byte = 0;
			$mask = 1;
			for ($span_x = 0; $span_x < $w; $span_x++) {
				$c = imagecolorat($img, $pos_x + $span_x, $pos_y + $span_y);
				if ($c == $color) {
					$byte |= $mask;
				}
				$mask <<= 1;
				if ($mask > 128) {
					$chars[] = $byte;
					$byte = 0;
					$mask = 1;
				}
			}
			if ($mask > 1) {
				$chars[] = $byte;
			}
		}
	}
}

$bytes_per_char = ceil($w / 8) * $h;
echo 'total bytes: ' . count($chars) . "\n";
echo "bytes per char: $bytes_per_char\n";
$cnt = 0;
echo "\$chars = [\n";

foreach($chars as $byte) {
	if ($cnt == 0) {
		echo "\t";
	}
	echo $byte . ', ';
	$cnt++;
	if ($cnt == $bytes_per_char) {
		echo "\n";
		$cnt = 0;
	}
}
echo "]\n";